Methods for operating radio frequency devices having transmit loopback functionality

ABSTRACT

A front end module having transmit loopback functionality may be operated by conducting a loopback signal from an output of a power amplifier to a receive port on a transmit loopback path and conducting a radio frequency receive signal from an antenna port to the receive port on a receive path. The transmit loopback path includes a first switch coupled between the output of the power amplifier and the receive port. The receive path includes a second switch coupled between the antenna port, where the receive port and is without the first switch.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND

In the digital pre-distortion power amplifier transmit portion of radiofrequency devices, the transmit output power can be sampled at theoutput of the power amplifier and then fed back to the receiver outputfor signal processing in the radio frequencytransceiver/baseband/system-on-a-chip. The sampled signal can then bemanipulated at baseband with digital signal processing such that apre-distorted version of the transmit radio frequency signal fed to theinput of the power amplifier results in a final power amplifier outputwith low distortion properties.

SUMMARY

The radio frequency path from the output of the power amplifier to thereceiver input can be referred to as the transmit loopback path. Incertain embodiments, the present disclosure relates to a method ofoperating a front end module having transmit loopback functionality. themethod comprises conducting on a transmit loopback path a loopbacksignal from an output of a power amplifier to a receive port. Thetransmit loopback path includes a first switch coupled between theoutput of the power amplifier and the receive port. The method furthercomprises conducting on a receive path a radio frequency receive signalfrom an antenna port to the receive port. The receive path includes asecond switch coupled between the antenna port and the receive port. Thereceive path is without the first switch.

In several embodiments, the method further comprises tapping a portionof the transmit loopback signal and attenuating the portion of thetransmit loopback signal.

In accordance with certain embodiments, the transmit loopback path andthe receive path share a common signal path between the receive port, afirst end of the first switch, and a first end of the second switch.

In accordance with certain embodiments, the method further comprisesclosing the first switch and opening the second switch when the frontend module operates in a transmit mode.

In several embodiments, the method further comprises opening the firstswitch and closing the second switch when the front end module operatesin a receive mode.

In certain embodiments, the present disclosure relates to a method ofoperating a front end module having transmit loopback functionality. Themethod comprises passing a loopback signal with a first switch in atransmit loopback path to a receive port of the front end module whenthe front end module is operating in a transmit mode. The first switchis configured to interrupt the transmit loopback path when the front endmodule is operating in a receive mode. The method further comprisespassing a radio frequency receive signal with a second switch in areceive path to the receive port when the front end module is operatingthe receive mode. The second switch is configured to interrupt thereceive path when the front end module is operating in the transmitmode. The receive path is free from the first switch.

In a number of embodiments, the method further comprises tapping aportion of the loopback signal and attenuating the portion of theloopback signal.

In several embodiments, the transmit loopback path and the receive pathshare a common signal path between the receive port, a first end of thefirst switch, and a first end of the second switch.

In certain embodiments, the present disclosure relates to a method ofoperating a front end module having transmit loopback functionality. Themethod comprises closing a first switch in a transmit loopback path andopening a second switch in a receive path when the front end module isoperating a transmit mode. The first switch is configured to pass aloopback signal from an output of a power amplifier to a receive port ofthe front end module and the second switch configured to interrupt thereceive path when the front end module is operating in the transmitmode. The method further comprises opening the first switch in thetransmit loopback path and closing the second switch in the receive pathwhen the front end module is operating in a receive mode. The firstswitch is configured to interrupt the transmit loopback path and thesecond switch is configured to pass a receive signal from an antennaport of the front end module to the receive port when the front endmodule is operating in the receive mode. The receive path is independentof the first switch.

In various embodiments, the method further comprises tapping a portionof the loopback signal and attenuating the portion of the loopbacksignal.

In several embodiments, the transmit loopback path and the receive pathshare a common signal path between the receive port, a first end of thefirst switch, and a first end of the second switch.

In certain embodiments, the method further comprises closing a thirdswitch and opening the first and second switches when the front endmodule operates in a low noise amplifier bypass mode. The third switchis configured to bypass the low noise amplifier and the second switchwhen the front end module is operating in the low noise amplifier bypassmode.

In accordance with certain embodiments, the transmit loopback path andthe receive path share a common signal path between the receive port, afirst end of the first switch, a first end of the second switch, and afirst end of the third switch.

In certain embodiments, the present disclosure relates to a method ofoperating a wireless device having transmit loopback functionality. Themethod comprises transmitting and receiving with an antenna radiofrequency signals, amplifying with a power amplifier a radio frequencysignal for transmission by the antenna, amplifying with a low noiseamplifier a radio frequency signal received by the antenna, andoperating in a transmit mode that includes closing a first switch in atransmit loopback path of a front end module and opening a second switchin a receive path of the front end module. The first switch isconfigured to pass a loopback signal from an output of a power amplifierto a receive port of the front end module. The method further comprisesoperating in a receive mode that includes opening the first switch inthe transmit loopback path and closing the second switch in the receivepath. The second switch is configured to pass a receive signal from anantenna port of the front end module to the receive port, the receivepath independent of the first switch.

In several embodiments, the radio frequency receive signal does not passthrough the first switch.

In accordance with certain embodiments, the method further comprisesinterrupting the loopback signal path when the front end module isoperating in the receive mode.

In accordance with some embodiments, the first switch is configured tointerrupt the loopback signal path when the front end module isoperating in the receive mode.

In a number of embodiments, the method further comprises interruptingthe receive signal path when the front end module is operating is thetransmit mode.

In several embodiments, the second switch is configured to interrupt thereceive signal path when the front end module is operating in thetransmit mode.

In some embodiments, method further comprises splitting with a splitterthe radio frequency receive signal for license assist access operation.

In certain embodiments, the present disclosure relates to a front endmodule having transmit loopback functionality. The front end modulecomprises a transmit loopback path configured to conduct a loopbacksignal from an output of a power amplifier to a receive port. Thetransmit loopback path includes a first switch coupled between theoutput of the power amplifier and the receive port and a receive pathconfigured to conduct a radio frequency receive signal from an antennaport to the receive port. The receive path includes a second switchcoupled between the antenna port and the receive port, where the receivepath is without the first switch.

In several embodiments, the front end module the transmit loopback pathfurther includes an attenuator and a coupler.

In accordance with certain embodiments, the transmit loopback path andthe receive path share a common signal path between the receive port, afirst end of the first switch, and a first end of the second switch.

In accordance with certain embodiments, the first switch is closed andthe second switch is open when the front end module operates in atransmit mode.

In accordance with some embodiments, the first switch is open and thesecond switch is closed when the front end module operates in a receivemode.

In certain embodiments, the present disclosure relates to a front endmodule having transmit loopback functionality. The front end modulecomprises a first switch in a transmit loopback path. The first switchis configured to pass a loopback signal to a receive port of the frontend module when the front end module is operating in a transmit mode.The first switch is configured to interrupt the transmit loopback pathwhen the front end module is operating in a receive mode. The front endmodule further comprises a second switch in a receive path. The secondswitch is configured to pass a radio frequency receive signal to thereceive port when the front end module is operating in the receive mode.The second switch is configured to interrupt the receive path when thefront end module is operating in the transmit mode. The receive path isfree from the first switch.

In a number of embodiments, a wireless device comprises the front endmodule.

In several embodiments, the transmit loopback path further includes anattenuator and a coupler.

In accordance with a number of embodiments, the transmit loopback pathand the receive path share a common signal path between the receiveport, a first end of the first switch, and a first end of the secondswitch.

In some embodiments, a system board for a wireless device comprises thefront end module.

In certain embodiments, the present disclosure relates to a front endmodule having transmit loopback functionality. The front end modulecomprises a power amplifier configured to amplify a radio frequencysignal for transmission by an antenna, a low noise amplifier configuredto amplify a radio frequency signal received by the antenna, and a firstswitch coupled between an output of the power amplifier and a receiveport of the front end module. A loopback signal path is formed betweenthe output of the power amplifier and the receive port and is configuredto carry a transmit loopback signal. The loopback signal path includesthe first switch. The front end module further comprises a second switchcoupled between an output of the low noise amplifier and the receiveport. A receive signal path is formed between an antenna port of thefront end module and the receive port and is configured to carry a radiofrequency receive signal. The receive signal path includes the low noiseamplifier and the second switch. The receive signal path excludes thefirst switch.

In a number of embodiments, a wireless device comprises the front endmodule.

In several embodiments, the loopback signal path and the receive signalpath share a common signal path between the receive port, a first end ofthe first switch, and a first end of the second switch.

In accordance with a number of embodiments, the front end module furthercomprises a splitter configured to split the radio frequency receivesignal for license assist access operation.

In certain embodiments, the present disclosure relates to a wirelessdevice having transmit loopback functionality. The wireless devicecomprises an antenna configured to transmit and receive radio frequencysignals, a power amplifier configured to amplify a radio frequencysignal for transmission by the antenna, a low noise amplifier configuredto amplify a radio frequency signal received by the antenna, and a frontend module having transmit loopback functionality. The front end moduleincludes a first switch coupled between an output of the power amplifierand a receive port of the front end module and a second switch coupledbetween an output of the low noise amplifier and the receive port. Aloopback signal path is formed between the output of the power amplifierand the receive port and is configured to carry a transmit loopbacksignal. The loopback signal path includes the first switch. A receivesignal path is formed between the antenna and the receive port and isconfigured to carry a radio frequency receive signal. The receive signalpath includes the low noise amplifier and the second switch. The receivesignal path excluding the first switch.

In various embodiments, the radio frequency receive signal does not passthrough the first switch.

In several embodiments, the first switch is configured to interrupt theloopback signal path when the front end module is operating in a receivemode.

In some embodiments, the second switch is configured to interrupt thereceive signal path when the front end module is operating is a transmitmode.

In certain embodiments, the wireless device further comprises a splitterconfigured to split the radio frequency receive signal for licenseassist access operation.

Certain aspects, advantages, and novel features of the inventions can bedescribed herein. It can be to be understood that not necessarily allsuch advantages may be achieved in accordance with any particularembodiment of the inventions disclosed herein. Thus, the inventionsdisclosed herein may be embodied or carried out in a manner thatachieves or selects one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will be described, by way of non-limitingexample, with reference to the accompanying drawings.

FIG. 1 is a block diagram of a first front end module with a transmitloopback path that is configured to transmit a radio frequency (RF)signal, according to certain embodiments.

FIG. 2 is a block diagram of the first front end module configured toreceive a RF signal, according to certain embodiments.

FIG. 3 is an exemplary circuit layout of the first front end module,according to certain embodiments.

FIG. 4 is a block diagram of a second front end module with a transmitloopback path that is configured to transmit a RF signal, according tocertain embodiments.

FIG. 5 is a block diagram of the second front end module configured toreceive a RF signal, according to certain embodiments.

FIG. 6 is an exemplary circuit layout of the second front end module,according to certain embodiments.

FIG. 7 is a block diagram of a third front end module with a transmitloopback path that is configured to transmit a RF signal, according tocertain embodiments.

FIG. 8 is a block diagram of the third front end module configured toreceive a RF signal, according to certain embodiments.

FIG. 9A is a flowchart illustrating a transmit process with loopbackfunctionality, according to certain embodiments.

FIG. 9B is a flowchart illustrating a receive process, according tocertain embodiments.

FIG. 10A is an exemplary block diagram of a module for use in a wirelessdevice, according to certain embodiments.

FIG. 10B is an exemplary block diagram of a system board assembly with afront end module including transmit loopback and other componentsdisposed on a system board, according to certain embodiments.

FIG. 11 is an exemplary block diagram illustrating a simplified wirelessdevice, according to certain embodiments

DETAILED DESCRIPTION

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Digital predistortion (DPD) is used to linearize the nonlinear responseof a power amplifier (PA) over its intended power range. In oneembodiment, digital signal processing techniques predistort a basebandsignal before modulation, up-conversion and amplification by the poweramplifier. The combination of the predistorted response and the poweramplifier response produces a more linear power amplifier response thanthe power amplifier response without the digital predistortion.

A radio frequency or microwave receive/transmit system is comprised of adigital pre-distortion/power amplifier/transmit/receive (DPD/PA/TX/RX)portion and a RF transceiver/baseband portion. The radio frequency ormicrowave receive/transmit system can be a wireless device, a portabletransceiver, a cell phone, a smartphone, tablet, a computer/laptopw/wireless, a pager, a global positioning system, a wireless accesspoint, a Wi-Fi access point, a wearable device, or like device.

In an embodiment, the digital pre-distortion/poweramplifier/transmit/receive portion comprises a front end module (FEM)that includes a power amplifier, a low noise amplifier (LNA), and atransmit/receive (TX/RX) switch. In an embodiment, the RFtransceiver/baseband portion of the system comprises a system on a chip(SOC).

In the digital pre-distortion/power amplifier/transmit/receive portionof the system, the transmit output power is sampled at the output of thepower amplifier and then fed back to the receive output of the front endmodule for signal processing in the RF transceiver/baseband portion ofthe system. The RF path from the output of the power amplifier to thereceive output is referred to as the transmit loopback path.

The sampled signal is then manipulated at baseband with digital signalprocessing (DSP) and used, at least in part, to pre-distort the transmitRF signal prior to amplification by the power amplifier and transmissionvia the antenna. In other words, the pre-distorted transmit RF signal isbased at least on the sampled signal. The pre-distorted transmit RFsignal is fed to the input of the power amplifier, which results in apower amplifier output with low distortion properties.

FIG. 1 is a block diagram of a front end module 100 with a transmitloopback path 32. As illustrated in FIG. 1, front end module 100 isconfigured to transmit a radio frequency (RF) signal. Front end module100 comprises a power amplifier module 10. Power amplifier module 10comprises a power amplifier 12 and a coupler/detector 14. Theupconverted/RF signal is placed at the transmit input to the poweramplifier 12. The power amplifier 12 outputs an amplified RF transmitsignal. The coupler/detector 14 taps a portion of the power amplifieroutput signal and sends it to the detector, which converts the RF signalto a direct current (DC) output at the detector output. The detectedpower level information is used to adjust the power level of the RFtransmit signal being input into the power amplifier 12 from the SOC.

Front end module 100 further comprises a TX/RX switch/low noiseamplifier module 16. TX/RX switch/low noise amplifier module 16comprises a coupler 18, a TX/RX switch 20, a low noise amplifier 22, aLNA output switch 24, a LNA bypass switch 30, an attenuator 26, and areceive & loopback switch 28. The TX/RX switch is switched to transmitand couples the amplified transmit signal from the power amplifier 12 toan antenna for transmission. Also during transmitting, the LNA outputswitch 24 is open, as well as the low noise amplifier bypass switch 30to prevent the low noise amplifier 22 from operating.

The loopback path 32 in the front end module 100 comprises the output ofthe power amplifier 12, the coupler 18, the attenuator 26, the receive &loopback switch 28, the receive & loopback output, and the connectingsignal routing to a receive & loopback output 17. The coupler 18comprises a power coupler and taps a portion of the transmit signalpower that is intended for the antenna path before the TX/RX switch 20.Attenuator 26 attenuates the coupled power, which is routed to thereceive & loopback output 17 of the front end module 100 via the receive& loopback switch 28.

In an embodiment, the receive & loopback switch 28 comprises a singlepole double throw (SPDT or SP2T) switch and is placed in the loopback(LB) position when the front end module 100 is in the transmit mode.

FIG. 2 is a block diagram of the front end module 100 where the frontend module 100 is configured to receive RF signals from the antenna. Inthe receive mode, the TX/RX switch 20 switched to receive, either theLNA output switch 24 or the LNA bypass switch 30 is in the closedposition, and the receive & loopback switch 28 is switched to receive.The RF receive signal is routed from the antenna, through the TX/RXswitch 20, and either the LNA bypass switch 30 or the low noiseamplifier 22 & LNA output switch 24, depending on which is selected. TheRF receive signal is further routed through the receive & loopbackswitch 28 to the receive & loopback output 17 of the front end module100.

FIG. 3 is an exemplary circuit layout 300 of the front end module 100illustrating a transmit loopback path 302 that begins at the poweramplifier output 15. The power amplifier output 15 receives the RFtransmit signal from the power amplifier 12. The transmit loopback path302 further comprises the RF path from the power amplifier output 15,through the attenuator 26, through the loopback switch 26 to the receive& loopback output 17. The transmit loopback path 302 passes near the lownoise amplifier output switch 24 and the LNA bypass switch 30. The poweramplifier output 15 and the receive & loopback output 17 are at oppositesides of the layout 300 and the transmit loopback path 302 extendsacross the layout 300 in a diagonal manner.

The receive & loopback switch 28 is in the receive path and switchesbetween the transmit loopback signal from the attenuator 26 when thefront end module 100 is transmitting and the receive signal from one ofthe LNA output switch or the LNA bypass switch 30 when the front endmodule 100 is receiving.

Implementation on-chip of the transmit loopback path 32, 302 with theloopback path architecture illustrated in FIGS. 1-3 generally has thefollowing issues:

1. The transmit loopback signal travels a long distance and across manyother signals in a highly-integrated chip. This is because the locationsof the coupler 18 and the receive & loopback output 17 are generallylocated far from one another for purposes of signal isolation.

2. The receive & loopback switch 28 is added in the receive path tomaintain RF impedance matching for the loopback path 32, 302 as well asthe receive path.

3. The receive & loopback switch 28 results in increased losses in thereceive path.

4. The transmit loopback path linearity is important because for DPD towork properly, an accurate replica of the TX signal at the PA outputmust be delivered to the RX output and subsequently the SOC forprocessing. If the TX loopback path is non-linear, the signal deliveredwill not be an accurate replica of the actual TX signal which is what isdesired in the system.

FIGS. 4-8 illustrate embodiments of transmit loopback path architecturethat overcome these issues.

FIG. 4 is a block diagram of a front end module 400 with a transmitloopback path 42. In FIG. 4, the frond end module 400 is illustrated intransmit mode and is configured to transmit a RF signal. Front endmodule 400 comprises the power amplifier module 10 including the poweramplifier 12 and the coupler 14. Front end module 400 further comprisesa TX/RX switch/low noise amplifier module 46. TX/RX switch/low noiseamplifier module 46 comprises the coupler 18, the TX/RX switch 20, thelow noise amplifier 22, the LNA output switch 24, the attenuator 26, anda loopback switch 48. The TX/RX switch is switched to transmit andcouples the amplified transmit signal from the power amplifier 12 to anantenna for transmission.

The transmit loopback path 42 in the front end module 400 comprises theoutput of the power amplifier 12, the coupler 18, the attenuator 26, theloopback switch 48, the receive & loopback output 17, and the connectingsignal routing. In TX/loopback mode, as illustrated in FIG. 4, the LNAoutput switch 24 and the LNA bypass switch 30 are both open.

The coupler 18 comprises a power coupler and taps a portion of thetransmit signal power that is intended for the antenna path before theTX/RX switch 20. Attenuator 26 attenuates the coupled power, which isrouted to the receive & loopback output of the front end module 400 viathe loopback switch 48.

FIG. 5 is a block diagram of the front end module 400 where the frontend module 400 configured to receive RF signals from the antenna. In thereceive mode, the TX/RX switch 20 switched to receive, either the LNAoutput switch 24 or the LNA bypass switch 30 is in the closed position,and the loopback switch 48 is open.

The RF receive signal is routed from the antenna, through the TX/RXswitch 20, and either the LNA bypass path or the low noise amplifier 22& LNA output switch 24, depending on which is selected, to the receive &loopback output 17 of the front end module 400.

Advantageously, the RF receive signal is not routed through anadditional switch, as in the transmit loopback path architecture offront end module 100.

The LNA output switch 24 that is in series with the LNA output alreadyexists for the purpose of LNA bypass mode. Thus, the RF path used forTX/loopback/DPD shares a portion of the already-existing RX path whilenot adding switches in the receive path for loopback purposes.Advantageously, the loopback signal routing is minimized, receive signalswitching and loss are also minimized, and optimum return loss ismaintained for both receive and transmit modes of operation.

The architecture of the transmit loopback path 42 solves the problemsassociated with the transmit loopback path 32. The signal routingon-chip for the transmit loopback path 42 is easier to implement thanthat of the transmit loopback path 32 because transmit loopback path 42makes use of a portion of the existing receive signal traces.Newly-added routes are relatively short and therefore also easy toimplement.

Good RF impedance matching is maintained for both receive path and theloopback signal path 42 because the RF switches 20, 24, and 48 areplaced such that characteristic impedance of each of the receive pathand the transmit loopback path 42 is maintained throughout.

There are no additional receive path losses associated with the SPDTreceive & loopback switch 28 that is needed at the back end of thereceive path for the transmit loopback path 32. The transmit loopbackpath 42 does not utilize a loopback switch in the receive path.

FIG. 6 is an exemplary circuit layout 600 of the front end module 400illustrating a transmit loopback path 602 that begins at the poweramplifier output 15. The transmit loopback path 602 further comprisesthe RF path through attenuator 26 through the loopback switch 48. Layout600 further illustrates a RF receive path 604. The RF receive path 604comprises a portion of the RF receive path for the front end module 400and extends from the low noise amplifier output switch 24 and the LNAbypass switch 30 to the receive & loopback output 17. The loopbackswitch 48 is not in the RF receive path, but the transmit loopbacksignal from the output of the loopback switch 48 travels along/sharesthe RF receive path 604 to the receive & loopback output 17.

The transmit loopback path 602 associated with the front end module 400is shorter than the transmit loopback path 302 associated with the frontend module 100. The transmit loopback path 602 utilizes existing tracesand routing on the layout 600. The loopback switch 48 in not in thereceive signal path.

Implementation on-chip of the transmit loopback path 42, 602 with theloopback path architecture illustrated in FIGS. 4-6 has the followingadvantages:

1. The transmit loopback signal travels a shorter distance across themany other signals in a highly-integrated chip. This reducescross-coupling.

2. The receive & loopback switch 48 not in the receive path. Because thereceive & loopback switch 48 not in the receive path, it is not neededto maintain RF impedance matching for the transmit loopback path 42, 602as well as the receive path.

3. The receive signal does not experience the increased loses that occurwith the receive & loopback switch 28 that is in the receive pathbecause the receive & loopback switch 48 is not in the receive path.

4. Linearity of the TX loopback path is unchanged from the previousarchitecture. This is because all active elements in the RX path areswitched out so that they will not affect linearity.

5. The loopback signal travels over a portion of the existing receivepath 604. This is an advantage in the layout 600 because separate signalrouting does not need to be provided, which simplifies the layout 600.In a highly-integrated IC, it is generally not possible to provide anisolated (desirable) path for the TX loopback due to space constraintsand the need to cross over other signal traces. In the previousimplementation, illustrated in FIG. 3, the TX loopback path isinevitably compromised due to space constraints, other signal routesthat are in the way, and the large distance that the signal travels.Being able to re-use a portion of the existing RF signal path is adistinct advantage.

FIGS. 7 and 8 illustrate another embodiment of the transmit loopbackarchitecture for a front end module 700 with a transmit loopback path58, where front end module 700 utilizes Wi-Fi and LTE-LAA (licensedassess assist) functionality. FIG. 7 illustrates the front end module700 in TX/loopback mode. The transmit loopback path 58 is similar to thetransmit loopback path 42 except the transmit loopback path 58 furtherincludes a splitter 54 and the transmit loopback signal is routedthrough a TX/RX switch/low noise amplifier module 76 from the output ofthe power amplifier 12, through the coupler 18, the attenuator 26, theloopback switch 48, the splitter 54 to the WLAN-RX & loopback output ofthe front end module 700. LAA RX is disabled when the front end module700 is in Wi-Fi transmit mode.

FIG. 8 illustrates the front end module 700 in receive mode. The antennareceives the RF signal. The RF receive signal travels through the TX/RXswitch 20 to either the LNA bypass switch 30 or the low noise amplifier22 and LNA output switch to the splitter 54. The splitter 54 sends aportion of the RF receive signal to the WLAN-RX & loopback output and aportion to the LAA-RX output, depending on the frequencies of the RFreceive signal.

The receive path does not include an additional switch, such as thereceive & loopback switch 28, in the receive path. Thus, the transmitloopback path 58 provides the same advantages discussed above withrespect to the transmit loopback path 42.

In an embodiment, front end modules 400, 700 communicate with logicarbitrator circuitry that controls the operation of one or more of theloopback switch 48, the TX/RX switch 20, the LNA output switch 24 andthe LNA bypass switch 30.

In an embodiment, the front end modules 400, 700 comprise remote 5 GHzFEM modules. In other embodiments, the front end modules 400, 700 canoperate from low-MHz to high-GHz frequency ranges.

In an embodiment, the front end module 400, 700 comprises the poweramplifier module 10 and the TX/RX switch/LNA module 46, 76. In anembodiment, the power amplifier module 10 is implemented using GaAs HBTand the TX/RX switch/LNA module 46, 76 is implemented using silicon oninsulator (SOI) in a chip scale package (CSP). In other embodiments, thefront end modules 400, 700 can be implemented using differenttechnologies, such as, but not limited to Si, SiGe, MOS, BJT, HBT,pHEMT, GaN, GaAs, InGaP GaAs HBT, MOSFET, SOI, Bulk CMOS, CMOS, and thelike. The Switch/LNA and PA functions may be implemented as separatechips or as a single highly-integrated IC.

The methods and apparatus described herein provide front end modules400, 700 with transmit/loopback functionality. FIG. 9A is a flowchartillustrating a transmit/loopback process 900 for a wireless devicecomprising the front end module 400, 700. At step 902, the process 900sets the TX/RX switch 20 to transmit. In an embodiment, a logicarbitrator controlled by baseband processing controls the switches.

At step 904, the front end module 400, 700 transmits the RF transmitsignal. At step 906, the coupler 18 taps a portion of the RF transmitsignal. At step 908, the attenuator 26 attenuates the portion of the RFtransmit signal to generate the transmit loopback signal. At step 910,the process 900 opens the LNA output switch 24 and the LNA bypass switch30. At step 912, the process 900 closes the transmit loopback switch 48to provide the transmit loopback signal to the receive & loopback output17 of the front end module 400, 700.

At step 914, the wireless device provides a pre-distorted transmitsignal to the power amplifier 12, where the pre-distorted transmitsignal is based at least in part on the transmit loopback signal.

FIG. 9B is a flowchart illustrating a receive process 950. At step 952,the process 950 sets the TX/RX switch 20 to receive. At step 954, theprocess 950 closes the LNA output switch 24 or the LNA bypass switch 30.At step 965, the process 950 opens the loopback switch 48 and the RFreceive signal travels through the TX/RX switch 20, either the pathdefined by the low noise amplifier 22 and LNA output switch 24 or thepath defined by the LNA bypass switch 30 to the receive & loopbackoutput 17 of the front end module 400, 700.

FIG. 10A is an exemplary block diagram of a module 1700 for use in awireless device, according to an embodiment. Module 1700 comprises afront end module (FEM) or front end integrated circuit (FEIC) 1704 thatincludes the front end module 400, 700 with transmit/loopbackfunctionality. Module 1700 further comprises one or more of a crystal1708, a system on a chip (SoC) 1702, connectivity 1706 to provide signalinterconnections, packaging 1712, such as for example, a packagesubstrate, for packaging of the circuitry, and other circuitry 1710,such as, for example, load capacitors associated with the crystal 1708,pre-filters, post filters modulators, demodulators, down converters, andthe like, as would be known to one of skill in the art of semiconductorfabrication in view of the disclosure herein. In an embodiment, themodule 1700 comprises a solution in a package (SiP).

FIG. 10B is an exemplary block diagram of a system board assembly 1000with the module 1700 that includes the front end module withtransmit/loopback functionality 400, 700 and other component(s) 80disposed on a system board 82, according to an embodiment. The systemboard 82 can be any suitable application board, such as a phone boardfor a mobile phone.

FIG. 11 is an exemplary block diagram illustrating a simplified wirelessdevice 1100 including an embodiment of the front end module 400, 700. Inan embodiment, the wireless device 1100 comprises a portabletransceiver, a cell phone, a smartphone, a tablet, a computer/laptopw/wireless, a pager, a global positioning system, a wireless accesspoint, a Wi-Fi access point, a wearable device, and the like.

The wireless device 1100 includes a speaker 1102, a display 1104, akeyboard 1106, and a microphone 1108, all connected to a basebandsubsystem 1110. A power source 1142, which may be a direct current (DC)battery or other power source, is also connected to the basebandsubsystem 1110 to provide power to the wireless device 1100. In aparticular embodiment, wireless device 1100 can be, for example but notlimited to, a portable telecommunication device such as a mobilecellular-type telephone. The speaker 1102 and the display 1104 receivesignals from baseband subsystem 1110, as known to those skilled in theart. Similarly, the keyboard 1106 and the microphone 1108 supply signalsto the baseband subsystem 1110.

The baseband subsystem 1110 includes a microprocessor (μP) 1120, memory1122, analog circuitry 1124, and a digital signal processor (DSP) 1126in communication via bus 1128. Bus 1128, although shown as a single bus,may be implemented using multiple busses connected as necessary amongthe subsystems within the baseband subsystem 1110. The basebandsubsystem 1110 may also include one or more of an application specificintegrated circuit (ASIC) 1132 and a field programmable gate array(FPGA) 1130.

The microprocessor 1120 and memory 1122 provide the signal timing,processing, and storage functions for wireless device 1100. The analogcircuitry 1124 provides the analog processing functions for the signalswithin baseband subsystem 1110. The baseband subsystem 1110 providescontrol signals to a transmitter 1150, a receiver 1170, and a poweramplifier 1180, for example.

It should be noted that, for simplicity, only the basic components ofthe wireless device 1100 are illustrated herein. The control signalsprovided by the baseband subsystem 1110 control the various componentswithin the wireless device 1100. Further, the function of thetransmitter 1150 and the receiver 1170 may be integrated into atransceiver.

The baseband subsystem 1110 also includes an analog-to-digital converter(ADC) 1134 and digital-to-analog converters (DACs) 1136 and 1138. Inthis example, the DAC 1136 generates in-phase (I) and quadrature-phase(Q) signals 1140 that are applied to a modulator 1152. The ADC 1134, theDAC 1136, and the DAC 1138 also communicate with the microprocessor1120, the memory 1122, the analog circuitry 1124, and the DSP 1126 viabus 1128. The DAC 1136 converts the digital communication informationwithin baseband subsystem 1110 into an analog signal for transmission tothe modulator 1152 via connection 1140. Connection 1140, while shown astwo directed arrows, includes the information that is to be transmittedby the transmitter 1150 after conversion from the digital domain to theanalog domain.

A crystal 1112 supplies clock information for the wireless device 1100.

The transmitter 1150 includes the modulator 1152, which modulates theanalog information on connection 1140 and provides a modulated signal toupconverter 1154. The upconverter 1154 transforms the modulated signalto an appropriate transmit frequency and provides the upconverted signalto the power amplifier 1180. The power amplifier 1180 amplifies thesignal to an appropriate power level for the system in which thewireless device 1100 is designed to operate. In an embodiment, the poweramplifier 1180 comprises the power amplifier module 10.

Details of the modulator 1152 and the upconverter 1154 have beenomitted, as they will be understood by those skilled in the art. Forexample, the data on connection 1140 is generally formatted by thebaseband subsystem 1110 into in-phase (I) and quadrature (Q) components.The I and Q components may take different forms and be formatteddifferently depending upon the communication standard being employed.

A front end module 1162 comprises the power amplifier 1180 and a TX/RXswitch/low noise amplifier (LNA) circuit 1172. In an embodiment, theswitch/low noise amplifier circuit 1172 comprises the TX/RX switch/lownoise amplifier module 46 with transmit/loopback architecture.

In an embodiment, the front end module 1162 comprises the front endmodule 400, 700. In an embodiment, front end module 1162 comprises afront end integrated circuit (FEIC).

The power amplifier 1180 supplies the amplified transmit signal to theswitch/low noise amplifier circuit 1172. The transmit signal is suppliedfrom the front end module 1162 to the antenna 1160 when the switch is inthe transmit mode.

A signal received by antenna 1160 will be directed from the switch/lownoise amplifier 1172 of the front end module 1162 to the receiver 1170when the switch is in the receive mode. The low noise amplifiercircuitry 1172 amplifies the received signal.

If implemented using a direct conversion receiver (DCR), thedownconverter 1174 converts the amplified received signal from an RFlevel to a baseband level (DC), or a near-baseband level (approximately100 kHz). Alternatively, the amplified received RF signal may bedownconverted to an intermediate frequency (IF) signal, depending on theapplication. The downconverted signal is sent to the filter 1176. Thefilter 1176 comprises a least one filter stage to filter the receiveddownconverted signal as known in the art.

The filtered signal is sent from the filter 1176 to the demodulator1178. The demodulator 1178 recovers the transmitted analog informationand supplies a signal representing this information via connection 1186to the ADC 1134. The ADC 1134 converts these analog signals to a digitalsignal at baseband frequency and transfers the signal via bus 1128 tothe DSP 1126 for further processing.

Terminology

Some of the embodiments described above have provided examples inconnection with mobile phones. However, the principles and advantages ofthe embodiments can be used for any other systems or apparatus that haveneeds for power amplifier systems.

Such a system or apparatus can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products, electronic test equipment, etc. Examples of theelectronic devices can also include, but are not limited to, memorychips, memory modules, circuits of optical networks or othercommunication networks, and disk driver circuits. The consumerelectronic products can include, but are not limited to, a mobile phonesuch as a smart phone, a telephone, a television, a computer monitor, acomputer, a hand-held computer, a laptop computer, a tablet computer, apersonal digital assistant (PDA), a PC card, a microwave, arefrigerator, an automobile, a stereo system, a cassette recorder orplayer, a DVD player, a CD player, a VCR, an MP3 player, a radio, acamcorder, a camera, a digital camera, a portable memory chip, a washer,a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novelmethods, apparatus, and systems described herein may be embodied in avariety of other forms; furthermore, various omissions, substitutions,and changes in the form of the methods and systems described herein maybe made without departing from the spirit of the disclosure. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosure.

What is claimed is:
 1. A method of operating a front end module,comprising: placing a transmit/receive switch in a transmit position tooperate the front end module in a transmit mode to conduct concurrentlyan output of a power amplifier on a transmit loopback path through apower coupler, an attenuator, and an output of a first switch to areceive port and on a transmit path through the power coupler to anantenna port; and placing the transmit/receive switch in a receiveposition to operate the front end module in a receive mode and toconduct on a receive path a radio frequency receive signal from theantenna port through a low noise amplifier and an output of a secondswitch to the receive port, the second switch coupled between the lownoise amplifier and the receive port, the receive path without the firstswitch, the transmit loopback path without the second switch, the outputof the first switch in the transmit loopback path in communication withthe output of the second switch.
 2. The method of claim 1 wherein thetransmit loopback path includes a power coupler, an attenuator, and thefirst switch.
 3. The method of claim 2 wherein the first switch iscoupled between an output of the attenuator and the receive port.
 4. Themethod of claim 3 wherein the power coupler is coupled between theoutput of the power amplifier and an input of the attenuator.
 5. Themethod of claim 2 further comprising tapping with the power coupler aportion of a power amplifier signal that is output from the poweramplifier and attenuating with the attenuator the portion of the poweramplifier signal to generate a loopback signal.
 6. The method of claim 1wherein the receive path includes a bypass switch coupled between theantenna port and the receive port to bypass the low noise amplifier. 7.A method of operating a front end module, comprising: placing thetransmit/receive switch in a transmit position to operate the front endmodule in a transmit mode; when the front end module is operating in atransmit mode, closing a first switch in a loopback path to pass throughan output of the first switch an attenuated first portion of a signaloutput from a power amplifier via a power coupler to a receive port andto conduct a second portion of the signal from the power amplifier to anantenna port and opening a second switch coupled between a low noiseamplifier and the receive port to interrupt a receive path at an outputof the second switch, the receive path independent of the first switch,the loopback path independent of the second switch, the output of thefirst switch in the loopback path in communication with the output ofthe second switch.
 8. The method of claim 7 wherein interrupting thereceive path includes opening a third switch in the receive path.
 9. Themethod of claim 8 further comprising closing the third switch andopening the first and second switches when the front end module operatesin a low noise amplifier bypass mode, the third switch configured tobypass the low noise amplifier and the second switch when the front endmodule is operating in the low noise amplifier bypass mode.
 10. Themethod of claim 7 further comprising opening the first switch in theloopback path and closing the second switch in the receive path when thefront end module is operating in a receive mode, the first switchconfigured to interrupt the loopback path and the second switchconfigured to pass a receive signal from an antenna port to the receiveport when the front end module is operating in the receive mode.
 11. Themethod of claim 7 wherein the loopback path includes a power coupler, anattenuator, and the first switch.
 12. The method of claim 11 wherein thefirst switch is coupled between the attenuator and the receive port, andthe power coupler is coupled between the power amplifier and theattenuator.
 13. The method of claim 7 further comprising: tapping with apower coupler in communication with the power amplifier a portion of thesignal output from the power amplifier; and attenuating with anattenuator in communication with the power coupler the portion of thesignal to form the attenuated first portion of the signal output fromthe power amplifier.
 14. The method of claim 7 wherein the loopback pathand the receive path share a common signal path between the receiveport, a first end of the first switch, and a first end of the secondswitch.
 15. A method of operating a wireless device, comprising:transmitting and receiving with an antenna radio frequency signals;amplifying with a power amplifier a radio frequency signal fortransmission by the antenna; and operating in a transmit mode thatincludes placing a transmit/receive switch in a transmit position,closing a first switch coupled between an attenuator and a receive port,tapping with a power coupler coupled between the power amplifier and theattenuator a portion of a signal from the power amplifier, attenuatingwith the attenuator the signal portion in a loopback path of a front endmodule to form a loopback signal that is received at the receive portvia an output of the first switch, conducting a transmit portion of thesignal from the power amplifier through the power coupler to an antennaport, and opening a second switch coupled between a low noise amplifierand the receive port to interrupt a receive path at an output of thesecond switch, the receive path independent of the first switch, theloopback path independent of the second switch, the output of the firstswitch in the loopback path in communication with the output of thesecond switch.
 16. The method of claim 15 wherein the first switch isconfigured to pass the loopback signal from an output of the poweramplifier to the receive port when the wireless device is operating inthe transmit mode.
 17. The method of claim 15 further comprisingamplifying with a low noise amplifier a radio frequency signal receivedby the antenna.
 18. The method of claim 17 further comprising operatingin a receive mode that includes opening the first switch in the loopbackpath and closing the second switch in the receive path, the secondswitch configured to pass a receive signal from the antenna to thereceive port.
 19. The method of claim 18 wherein the radio frequencyreceive signal does not pass through the first switch.
 20. The method ofclaim 15 wherein the loopback path and the receive path share a commonsignal path between the receive port, a first end of the first switch,and a first end of the second switch.